The original goal of this project was to develop, characterize and maintain a feline model of human NPC, to provide NPC tissues and kittens to other investigators, and to evaluate various treatment modalities. The overall goal of this Competitive Renewal is essentially the same. The specific aims of this project are 1) to continue to maintain this colony of feline NPC and continue to make this model available to other investigators, 2) to further characterize the feline model by using antibodies generated against the feline NPC1 protein, and 3) to continue to evaluate a ganglioside synthesis inhibitor as therapy for NPC, because a pilot study has shown decreased ganglioside storage in cats treated with this inhibitor. NPC in human beings as well as in the feline model, is an autosomal recessive lysosomal storage disorder with a variety of clinical features including organomegaly, progressive neurologic abnormalities possibly related to neuronal ganglioside storage, and premature death. The primary cytologic defect is associated with defective intracellular transport of unesterified cholesterol. The NPC1 protein is now thought to also play a role in ganglioside transport. The gene responsible for the most common type of human NPC (NPC1) has been identified. Complementation studies using cat and human NPC fibroblasts support that the gene responsible for NPC in the feline model is orthologus to human NPC1. Feline specific PCR primers were generated and designed to amplify six overlapping bands which span the entire feline NPC open reading frame. The predicted feline amino acid sequence shows 91% homology to the human NPC1 protein. A single base substitution, resulting in a conserved cysteine to serine substitution, has been identified in all NPC affected cats evaluated, and is in the same area as several of the point mutations reported in human beings. Carriers are heterozygous for the same allele. A PCR-based assay has been developed that quickly and accurately identifies carriers, as well as affected kittens. This model will provide a unique and valuable resource with which to evaluate treatment modalities for NPC. Increased numbers of NPC-affected kittens will now be available, since carrier detection eliminates time-consuming breeding trials. Approximately 12 female and three male carriers will be maintained at CSU, with the goal of producing 15 to 20 affected kittens per year. Additional breeders and affected kittens will be made available to other investigators.